1. Field of the Invention
The present invention generally relates to liquid crystal display (LCD) devices.
2. Description of Related Art
Recently, liquid crystal display (LCD) devices are being used as large size computer monitors and as televisions. To realize a high quality LCD device, high transmittance, high contrast ratio and wide view angle are the main technical parameters that typically are the most highly desired. Vertical alignment (VA) mode LCD devices in normally black mode can provide a sufficiently dark off-state, so it is relatively easy to fabricate an LCD device with high a contrast ratio. To provide a wide view angle range in VA mode, a domain dividing structure typically is used. Therefore, in order to obtain a wide view angle ability in VA mode, control of LC domains (the formation of multi-domain vertical alignment (MVA)) is considered important, especially when the voltage is applied.
Fujitsu Ltd. disclosed an MVA LCD using physical protrusions that was discussed in SID Technical Digest, vol. 29, p. 1077 (1998), Fujitsu Science Technical Journal, vol. 35, p. 221 (1999), and which is also generally disclosed in U.S. Pat. No. 6,424,398 B1. The chevron-patterned protrusions of these disclosures are created on the top and bottom substrates to form four-domain LCD cells in multiple independent directions. The devices provide a high contrast ratio (higher than 300:1), and a view angle wider than 160 degrees using biaxial compensation films. Since the horizontal gap between the upper and the lower protrusions must be less than 30 μm in order to obtain good performance, pixel alignment needs high precision. Thus, the design specification and preparation processes are quite complex and the aperture ratio is limited.
International Business Machines (IBM) Corp. proposed a ridge and fringe-field multi-domain homeotropic (RFF-MH) mode, in which one substrate includes protrusions and the other includes slits to form the multi-domains. Such was published in Material Research Society Symposium Proceedings, vol. 559, p. 275 (1999), and was generally disclosed in U.S. Pat. No. 6,493,050 B1. The device has a contrast ratio larger than 250:1, requires higher driving voltages and requires a long response time.
As a simplified technology of the above MVA and RFF-MH technologies, Samsung Electronics Co. proposed a patterned vertical alignment (PVA) mode, in which only slits were used to produce a multi-domain structure under electric fields. As described in their U.S. Pat. No. 6,285,431 B2 and U.S. Pat. No. 6,570,638 B2, horizontal, vertical or oblique shaped slits are fabricated to form zig-zag or W-shaped ITO patterning structure. Tetragonal rings also are discussed in U.S. Pat. Nos. 6,512,568 and 6,577,366.
In the above-mentioned modes, two linear polarizers are usually used. Additionally, Iwamoto et al have reported an MVA mode using circular polarizers as published in the 9th International Display Workshops, p. 85 (Hiroshima, Japan, Dec. 4-6, 2002) and Japanese Journal of Applied Physics, Vol. 41, p. L1383 (2002).